body {
  width: 90%;
  max-width: 900px;
  margin: 0 auto;
}

.box {
  float: left;
  width: 150px;
  height: 100px;
  margin: 15px;
  padding: 10px;
  background: rgb(255, 209, 209);
  border-radius: 8px;
}

.wrapper {
  background: rgb(203, 253, 162);
  /* 使用非 visible的值产生清除浮动的作用，具有副作用*/
  /* overflow: auto; */
  /* display: flow-root; */
}

.cl {
  /* clear: left; */
  /* clear: right; */
  clear: both;
}

.wrapper::after{
    content: '';
    display: block;
    clear:both;
}
